1 General Packet Radio General Packet Radio Service (GPRS) Service (GPRS) Miao Lu Miao Lu ([email protected]) ([email protected]) Nancy Samaan Nancy Samaan ([email protected]) ([email protected]) SITE, Ottawa University SITE, Ottawa University CSI 5171 (95.533) Network Architectures, Services, Protocols and Standards
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1 General Packet Radio Service (GPRS) Miao Lu ([email protected]) Nancy Samaan ([email protected]) SITE, Ottawa University CSI 5171 (95.533) Network.
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General Packet Radio Service General Packet Radio Service (GPRS)(GPRS)
• IP-based backbone network Old components in GSM upgraded for GPRS
services:
• HLR
• MSC/VLR
• Mobile Station
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GPRS ArchitectureGPRS ArchitectureSGSN – Serving GPRS Support NodeSGSN – Serving GPRS Support Node
At the same hierarchical level as the MSC. Transfers data packets between mobile
stations and GGSNs. Keeps track of the individual MSs’ location
and performs security functions and access control.
Participates into routing, as well as mobility management functions.
Detects and registers new GPRS mobile stations located in its service area
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GPRS ArchitectureGPRS ArchitectureGGSN – Gateway GPRS Support NodeGGSN – Gateway GPRS Support Node
Provides inter-working between PLMN and external packet-switched networks.
Converts the GPRS packets from SGSN into the appropriate packet data protocol format (e.g., IP or X.25) and sends out on the corresponding packet data network.
Participates into the mobility management. Maintains the location information of the mobile
stations that are using the data protocols provided by that GGSN.
Collects charging information for billing purpose.
Tunnels of data and signaling messages between GPRS support nodes.
Protocol architecture based on the Internet Protocol (IP).
GTP (GPRS Tunneling Protocol) used to tunnel user data and signaling between GPRS Support Nodes. All PDP (Packet Data Protocol) PDUs (Protocol Data Units) shall be encapsulated by GTP.
GPRS packets routing information and handset location information are updated in other GSM components, such as HLR.
SGSN communicates with GGSN. GGSN sends the packets to PDNs.
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AgendaAgenda
IntroductionIntroduction
Part IPart I
• GPRS Architecture
Part IIPart II Bearer and Supplementary Services Mobility Management GPRS Limitations
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Bearer and Supplementary Services of GPRSBearer and Supplementary Services of GPRS
The bearer servicesbearer services of GPRS offer end-to-end packet switched data transfer.
Two different kinds of bearer services :
• PTP (Point-to-point) services
• PTM (Point-to-multipoint) services
• Supplementary ServicesSupplementary Services : SMS call, call forwarding unconditional (CFU), call forwarding on mobile subscriber not reachable (CFNRc), and closed user group (CUG) .
Two types :Connection-Oriented Network Service (PTP-CONS) :Connection-Oriented Network Service (PTP-CONS) :• A logical relation is established between users.
• supports bursty transactional or interactive APs based on X.25.
• Multiple packets are sent between a single source and destination.
• Examples : Credit card validations, Telnet, and Database access.
ConnectionLess Network Service (PTP-CLNS) :ConnectionLess Network Service (PTP-CLNS) :• A datagram type service based on the connectionless network protocol (ex: IP).
• Supports bursty non-interactive applications.
• No logical link required between users.
• Each packet is sent is independent of other packets.
• Examples :Electronic mail, Internet ‘s World Wide Web.
enables the transmission of a single message to multiple destinations. Multicast service (PTM-M): Multicast service (PTM-M): • Addressed to all subscribers in a geographical area group identifier
indicating whether to all subscribers or to a specific PTM group • Example : News, Weather and Traffic reports.
Group call service (PTM-G): Group call service (PTM-G): • Only a predefined group of subscribers controlled by a multicast
server will receive the message transmitted.
• Group members must join the PTM-G call.
• Real time delivery.
• Example: Conferencing services. IP Multicast (IP-M ):IP Multicast (IP-M ):• Messages are transmitted to a specific group.
• Group members must join the IP-M call.
• Real time delivery.
• Examples : Live multimedia transmissions.
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Mobility Management Mobility Management
• Mobility management is the means by which GPRS keeps track of a mobile subscriber location while connected to the Network.
International Mobile station Equipment Identity (IMEI) : (IMEI) : Specified for each equipment by the manufacturer
International Mobile Subscriber Identity (IMSI):(IMSI):
• It is stored in the subscriber identity module (SIM). Temporary International Mobile Subscriber Identity
(TMSI):(TMSI):
• assigned by the VLR. Packet Temporary Mobile Subscriber Identity (P-TMSI):(P-TMSI):
• (during attachment by the SGSN) . Temporary Link Layer Identifier (TLLI):(TLLI):
• During the attachment phase , a TLLI is randomly generated by mobile.
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Mobility Management Mobility Management GPRS service Areas[8]GPRS service Areas[8]
SA : Service Area
RA: Routing Area
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Explicit Detach
Mobility Management Mobility Management Mobility Management StatesMobility Management States
IDLE
READY
STANDBY
GPRS Attach GPRS Detach
Timer expiry/Force STANDBY/
Abnormal RLC condition
PDU Transmission
/Reception
reachable mobile
unreachable mobile
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IDLE StateIDLE State GPRS MS is unreachable - MS may receive PTM-M message
READY stateREADY state
MS can send and receive PDP PDU, and receive PTM-P and PTM-G data. MS informs SGSN when it changes cells. A timer monitors the ready state and upon its expiry, the MS is put on standby.
STANDBY StateSTANDBY State
MS is attached to GPRS MM. - MS and SGSN have established MM contexts. MS can receive PTM-M and PTM-G data (i.e. can receive paging message) MS execute MM procedure to inform SGSN when MS enter a new RA
PTP data reception and transmission, and PTM-G data transmission are not possible MS does not inform SGSN when a change of cell in the same RA
Mobility Management Mobility Management Mobility Management States Mobility Management States (cont.)(cont.)
• An MS can connect to the GPRS network by requesting a GPRS attachattach procedure.
• The outcome is the establishment of a logical link between the MS and a single SGSN and the creation of a mobility mobility management contextmanagement context.
• The logical link is uniquely defined by the identifier TLLI TLLI and is used subsequently in messages exchanged between the MS and SGSN.
• This identifier is changed when the MS is served by a new SGSN.
Before a mobile station can use GPRS services, it must register with an SGSN of the GPRS network. The network checks if the user is authorized, copies the user profile from the HLR to the SGSN, and assigns a packet temporary mobile subscriber identity (P-TMSI) to the user.
Steps :
• Inform the network for the MS’s request to be active
• Network checks the Ms’s identity
• Download MS’s subscription information from HLR to SGSN.
• Support of GPRS Mobile Terminate by Terminals is Not Ensured
• Packet switching means that data packets can traverse different routes and then be reassembled in their final destination leading to potential transit delays affecting the Quality of Service.
• Operators may decide to charge based on time rather than volume, which may destroy the cost advantage that GPRS provides today.
• Requires major network modifications: Many network elements to be upgraded and totally new to be introduced
• Expensive: Not much time for invest to be returned due to upcoming 3rd generation technology
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References (papers)References (papers)
[1] Dale R. Shelton, “General Packet Radio Service”, Aether Systems, Incorporated, 2001
[2] Agilent Technologies, “Understanding General Packet Radio Service (GPRS)”, Technical report, 2001.
[3] Christian Bettstetter, Hans-J¨org V¨ogel and J¨org Ebersp¨acher, “GSM Phase 2+ General Packet Radio Service GPRS: Architecture, Protocols, and Air Interface”, IEEE Communication Surveys, vol. 2, n. 3, 1999.
[4] ETSI, “GSM 02.60 Digital cellular telecommunications system (Phase2+): General Packet Radio Service, Service Description Stage 1”.
[5] ETSI, “GSM 03.60 Digital cellular telecommunications system (Phase2+); General Packet Radio Service, Service Description Stage 2”, 1998.
[6] L. Logrippo D. Amyot, N.Hart and P. Forhan, “Formal Specification and Validation using a Scenario-Based Approach: The GPRS Group-Call Example”,ObjecTime Workshop on Research in OO Real-Time Modeling, Ottawa, Canada, pp. 99–118, Jan. 1998
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References (papers)References (papers)
[7] B. Ghribi L. Andriantsiferana and L. Logrippo, “Prototyping and Formal Requirement Validation of GPRS: A Mobile Data Packet Radio Service for GSM”, Proceedings of 7th Int. Working Confrence on Dependable Computing For Critical Applications (DCCA-7), san Jose, California,USA, pp. 99–118, Jan. 1999.
[8] B. Ghribiand L. Logrippo, “Understanding GPRS: The GSM Packet Radio Service”, Computer Networks, vol. 34, pp. 763–779, 2000.
[9] Herman Rao Yi-Bing Lin and Imrich Chlamtac, “General Packet Radio Service (GPRS): Architecture, Interfaces, and Deployment”, Journal of Wireless Communiations and Mobile Computing, vol. 1, n. 1, pp. 77–92, 2001.